/*
 * Copyright (C) 2007 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkElementIndex;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkPositionIndex;
import static com.google.common.base.Preconditions.checkPositionIndexes;
import static com.google.common.collect.CollectPreconditions.checkNonnegative;
import static com.google.common.collect.ObjectArrays.checkElementsNotNull;
import static com.google.common.collect.RegularImmutableList.EMPTY;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.DoNotCall;
import com.google.errorprone.annotations.InlineMe;

import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.Serializable;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.RandomAccess;
import javax.annotation.CheckForNull;

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A {@link List} whose contents will never change, with many other important properties detailed at
 * {@link ImmutableCollection}.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/ImmutableCollectionsExplained"> immutable collections</a>.
 *
 * @author Kevin Bourrillion
 * @see ImmutableMap
 * @see ImmutableSet
 * @since 2.0
 */
@GwtCompatible(serializable = true, emulated = true)
@SuppressWarnings("serial") // we're overriding default serialization
@ElementTypesAreNonnullByDefault
public abstract class ImmutableList<E> extends ImmutableCollection<E>
        implements List<E>, RandomAccess
{
    /**
     * Returns the empty immutable list. This list behaves and performs comparably to {@link
     * Collections#emptyList}, and is preferable mainly for consistency and maintainability of your
     * code.
     *
     * <p><b>Performance note:</b> the instance returned is a singleton.
     */
    // Casting to any type is safe because the list will never hold any elements.
    @SuppressWarnings("unchecked")
    public static <E> ImmutableList<E> of()
    {
        return (ImmutableList<E>) EMPTY;
    }

    /**
     * Returns an immutable list containing a single element. This list behaves and performs
     * comparably to {@link Collections#singletonList}, but will not accept a null element. It is
     * preferable mainly for consistency and maintainability of your code.
     *
     * @throws NullPointerException if {@code element} is null
     */
    public static <E> ImmutableList<E> of(E element)
    {
        return construct(element);
    }

    /**
     * Returns an immutable list containing the given elements, in order.
     *
     * @throws NullPointerException if any element is null
     */
    public static <E> ImmutableList<E> of(E e1, E e2)
    {
        return construct(e1, e2);
    }

    /**
     * Returns an immutable list containing the given elements, in order.
     *
     * @throws NullPointerException if any element is null
     */
    public static <E> ImmutableList<E> of(E e1, E e2, E e3)
    {
        return construct(e1, e2, e3);
    }

    /**
     * Returns an immutable list containing the given elements, in order.
     *
     * @throws NullPointerException if any element is null
     */
    public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4)
    {
        return construct(e1, e2, e3, e4);
    }

    /**
     * Returns an immutable list containing the given elements, in order.
     *
     * @throws NullPointerException if any element is null
     */
    public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4, E e5)
    {
        return construct(e1, e2, e3, e4, e5);
    }

    /**
     * Returns an immutable list containing the given elements, in order.
     *
     * @throws NullPointerException if any element is null
     */
    public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4, E e5, E e6)
    {
        return construct(e1, e2, e3, e4, e5, e6);
    }

    /**
     * Returns an immutable list containing the given elements, in order.
     *
     * @throws NullPointerException if any element is null
     */
    public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7)
    {
        return construct(e1, e2, e3, e4, e5, e6, e7);
    }

    /**
     * Returns an immutable list containing the given elements, in order.
     *
     * @throws NullPointerException if any element is null
     */
    public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8)
    {
        return construct(e1, e2, e3, e4, e5, e6, e7, e8);
    }

    /**
     * Returns an immutable list containing the given elements, in order.
     *
     * @throws NullPointerException if any element is null
     */
    public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9)
    {
        return construct(e1, e2, e3, e4, e5, e6, e7, e8, e9);
    }

    /**
     * Returns an immutable list containing the given elements, in order.
     *
     * @throws NullPointerException if any element is null
     */
    public static <E> ImmutableList<E> of(
            E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10)
    {
        return construct(e1, e2, e3, e4, e5, e6, e7, e8, e9, e10);
    }

    /**
     * Returns an immutable list containing the given elements, in order.
     *
     * @throws NullPointerException if any element is null
     */
    public static <E> ImmutableList<E> of(
            E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10, E e11)
    {
        return construct(e1, e2, e3, e4, e5, e6, e7, e8, e9, e10, e11);
    }

    // These go up to eleven. After that, you just get the varargs form, and
    // whatever warnings might come along with it. :(

    /**
     * Returns an immutable list containing the given elements, in order.
     *
     * <p>The array {@code others} must not be longer than {@code Integer.MAX_VALUE - 12}.
     *
     * @throws NullPointerException if any element is null
     * @since 3.0 (source-compatible since 2.0)
     */
    @SafeVarargs // For Eclipse. For internal javac we have disabled this pointless type of warning.
    public static <E> ImmutableList<E> of(
            E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10, E e11, E e12, E... others)
    {
        checkArgument(
                others.length <= Integer.MAX_VALUE - 12, "the total number of elements must fit in an int");
        Object[] array = new Object[12 + others.length];
        array[0] = e1;
        array[1] = e2;
        array[2] = e3;
        array[3] = e4;
        array[4] = e5;
        array[5] = e6;
        array[6] = e7;
        array[7] = e8;
        array[8] = e9;
        array[9] = e10;
        array[10] = e11;
        array[11] = e12;
        System.arraycopy(others, 0, array, 12, others.length);
        return construct(array);
    }

    /**
     * Returns an immutable list containing the given elements, in order. If {@code elements} is a
     * {@link Collection}, this method behaves exactly as {@link #copyOf(Collection)}; otherwise, it
     * behaves exactly as {@code copyOf(elements.iterator()}.
     *
     * @throws NullPointerException if {@code elements} contains a null element
     */
    public static <E> ImmutableList<E> copyOf(Iterable<? extends E> elements)
    {
        checkNotNull(elements); // TODO(kevinb): is this here only for GWT?
        return (elements instanceof Collection)
                ? copyOf((Collection<? extends E>) elements)
                : copyOf(elements.iterator());
    }

    /**
     * Returns an immutable list containing the given elements, in order.
     *
     * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
     * safe to do so. The exact circumstances under which a copy will or will not be performed are
     * undocumented and subject to change.
     *
     * <p>Note that if {@code list} is a {@code List<String>}, then {@code ImmutableList.copyOf(list)}
     * returns an {@code ImmutableList<String>} containing each of the strings in {@code list}, while
     * ImmutableList.of(list)} returns an {@code ImmutableList<List<String>>} containing one element
     * (the given list itself).
     *
     * <p>This method is safe to use even when {@code elements} is a synchronized or concurrent
     * collection that is currently being modified by another thread.
     *
     * @throws NullPointerException if {@code elements} contains a null element
     */
    public static <E> ImmutableList<E> copyOf(Collection<? extends E> elements)
    {
        if (elements instanceof ImmutableCollection)
        {
            @SuppressWarnings("unchecked") // all supported methods are covariant
            ImmutableList<E> list = ((ImmutableCollection<E>) elements).asList();
            return list.isPartialView() ? ImmutableList.<E>asImmutableList(list.toArray()) : list;
        }
        return construct(elements.toArray());
    }

    /**
     * Returns an immutable list containing the given elements, in order.
     *
     * @throws NullPointerException if {@code elements} contains a null element
     */
    public static <E> ImmutableList<E> copyOf(Iterator<? extends E> elements)
    {
        // We special-case for 0 or 1 elements, but going further is madness.
        if (!elements.hasNext())
        {
            return of();
        }
        E first = elements.next();
        if (!elements.hasNext())
        {
            return of(first);
        }
        else
        {
            return new ImmutableList.Builder<E>().add(first).addAll(elements).build();
        }
    }

    /**
     * Returns an immutable list containing the given elements, in order.
     *
     * @throws NullPointerException if {@code elements} contains a null element
     * @since 3.0
     */
    public static <E> ImmutableList<E> copyOf(E[] elements)
    {
        return (elements.length == 0)
                ? ImmutableList.<E>of()
                : ImmutableList.<E>construct(elements.clone());
    }

    /**
     * Returns an immutable list containing the given elements, sorted according to their natural
     * order. The sorting algorithm used is stable, so elements that compare as equal will stay in the
     * order in which they appear in the input.
     *
     * <p>If your data has no duplicates, or you wish to deduplicate elements, use {@code
     * ImmutableSortedSet.copyOf(elements)}; if you want a {@code List} you can use its {@code
     * asList()} view.
     *
     * <p><b>Java 8 users:</b> If you want to convert a {@link java.util.stream.Stream} to a sorted
     * {@code ImmutableList}, use {@code stream.sorted().collect(toImmutableList())}.
     *
     * @throws NullPointerException if any element in the input is null
     * @since 21.0
     */
    public static <E extends Comparable<? super E>> ImmutableList<E> sortedCopyOf(
            Iterable<? extends E> elements)
    {
        Comparable<?>[] array = Iterables.toArray(elements, new Comparable<?>[0]);
        checkElementsNotNull((Object[]) array);
        Arrays.sort(array);
        return asImmutableList(array);
    }

    /**
     * Returns an immutable list containing the given elements, in sorted order relative to the
     * specified comparator. The sorting algorithm used is stable, so elements that compare as equal
     * will stay in the order in which they appear in the input.
     *
     * <p>If your data has no duplicates, or you wish to deduplicate elements, use {@code
     * ImmutableSortedSet.copyOf(comparator, elements)}; if you want a {@code List} you can use its
     * {@code asList()} view.
     *
     * <p><b>Java 8 users:</b> If you want to convert a {@link java.util.stream.Stream} to a sorted
     * {@code ImmutableList}, use {@code stream.sorted(comparator).collect(toImmutableList())}.
     *
     * @throws NullPointerException if any element in the input is null
     * @since 21.0
     */
    public static <E> ImmutableList<E> sortedCopyOf(
            Comparator<? super E> comparator, Iterable<? extends E> elements)
    {
        checkNotNull(comparator);
        @SuppressWarnings("unchecked") // all supported methods are covariant
        E[] array = (E[]) Iterables.toArray(elements);
        checkElementsNotNull(array);
        Arrays.sort(array, comparator);
        return asImmutableList(array);
    }

    /**
     * Views the array as an immutable list. Checks for nulls; does not copy.
     */
    private static <E> ImmutableList<E> construct(Object... elements)
    {
        return asImmutableList(checkElementsNotNull(elements));
    }

    /**
     * Views the array as an immutable list. Does not check for nulls; does not copy.
     *
     * <p>The array must be internally created.
     */
    static <E> ImmutableList<E> asImmutableList(Object[] elements)
    {
        return asImmutableList(elements, elements.length);
    }

    /**
     * Views the array as an immutable list. Does not check for nulls.
     */
    static <E> ImmutableList<E> asImmutableList(@Nullable Object[] elements, int length)
    {
        if (length == 0)
        {
            return of();
        }
        return new RegularImmutableList<E>(elements, length);
    }

    ImmutableList()
    {
    }

    // This declaration is needed to make List.iterator() and
    // ImmutableCollection.iterator() consistent.
    @Override
    public UnmodifiableIterator<E> iterator()
    {
        return listIterator();
    }

    @Override
    public UnmodifiableListIterator<E> listIterator()
    {
        return listIterator(0);
    }

    @SuppressWarnings("unchecked")
    @Override
    public UnmodifiableListIterator<E> listIterator(int index)
    {
        checkPositionIndex(index, size());
        if (isEmpty())
        {
            return (UnmodifiableListIterator<E>) EMPTY_ITR;
        }
        else
        {
            return new Itr<E>(this, index);
        }
    }

    /**
     * A singleton implementation of iterator() for the empty ImmutableList.
     */
    private static final UnmodifiableListIterator<Object> EMPTY_ITR =
            new Itr<Object>(RegularImmutableList.EMPTY, 0);

    static class Itr<E> extends AbstractIndexedListIterator<E>
    {
        private final ImmutableList<E> list;

        Itr(ImmutableList<E> list, int index)
        {
            super(list.size(), index);
            this.list = list;
        }

        @Override
        protected E get(int index)
        {
            return list.get(index);
        }
    }

    @Override
    public int indexOf(@CheckForNull Object object)
    {
        return (object == null) ? -1 : Lists.indexOfImpl(this, object);
    }

    @Override
    public int lastIndexOf(@CheckForNull Object object)
    {
        return (object == null) ? -1 : Lists.lastIndexOfImpl(this, object);
    }

    @Override
    public boolean contains(@CheckForNull Object object)
    {
        return indexOf(object) >= 0;
    }

    // constrain the return type to ImmutableList<E>

    /**
     * Returns an immutable list of the elements between the specified {@code fromIndex}, inclusive,
     * and {@code toIndex}, exclusive. (If {@code fromIndex} and {@code toIndex} are equal, the empty
     * immutable list is returned.)
     */
    @Override
    public ImmutableList<E> subList(int fromIndex, int toIndex)
    {
        checkPositionIndexes(fromIndex, toIndex, size());
        int length = toIndex - fromIndex;
        if (length == size())
        {
            return this;
        }
        else if (length == 0)
        {
            return of();
        }
        else
        {
            return subListUnchecked(fromIndex, toIndex);
        }
    }

    /**
     * Called by the default implementation of {@link #subList} when {@code toIndex - fromIndex > 1},
     * after index validation has already been performed.
     */
    ImmutableList<E> subListUnchecked(int fromIndex, int toIndex)
    {
        return new SubList(fromIndex, toIndex - fromIndex);
    }

    class SubList extends ImmutableList<E>
    {
        final transient int offset;
        final transient int length;

        SubList(int offset, int length)
        {
            this.offset = offset;
            this.length = length;
        }

        @Override
        public int size()
        {
            return length;
        }

        @Override
        @CheckForNull
        @Nullable
        Object[] internalArray()
        {
            return ImmutableList.this.internalArray();
        }

        @Override
        int internalArrayStart()
        {
            return ImmutableList.this.internalArrayStart() + offset;
        }

        @Override
        int internalArrayEnd()
        {
            return ImmutableList.this.internalArrayStart() + offset + length;
        }

        @Override
        public E get(int index)
        {
            checkElementIndex(index, length);
            return ImmutableList.this.get(index + offset);
        }

        @Override
        public ImmutableList<E> subList(int fromIndex, int toIndex)
        {
            checkPositionIndexes(fromIndex, toIndex, length);
            return ImmutableList.this.subList(fromIndex + offset, toIndex + offset);
        }

        @Override
        boolean isPartialView()
        {
            return true;
        }
    }

    /**
     * Guaranteed to throw an exception and leave the list unmodified.
     *
     * @throws UnsupportedOperationException always
     * @deprecated Unsupported operation.
     */
    @CanIgnoreReturnValue
    @Deprecated
    @Override
    @DoNotCall("Always throws UnsupportedOperationException")
    public final boolean addAll(int index, Collection<? extends E> newElements)
    {
        throw new UnsupportedOperationException();
    }

    /**
     * Guaranteed to throw an exception and leave the list unmodified.
     *
     * @throws UnsupportedOperationException always
     * @deprecated Unsupported operation.
     */
    @CanIgnoreReturnValue
    @Deprecated
    @Override
    @DoNotCall("Always throws UnsupportedOperationException")
    public final E set(int index, E element)
    {
        throw new UnsupportedOperationException();
    }

    /**
     * Guaranteed to throw an exception and leave the list unmodified.
     *
     * @throws UnsupportedOperationException always
     * @deprecated Unsupported operation.
     */
    @Deprecated
    @Override
    @DoNotCall("Always throws UnsupportedOperationException")
    public final void add(int index, E element)
    {
        throw new UnsupportedOperationException();
    }

    /**
     * Guaranteed to throw an exception and leave the list unmodified.
     *
     * @throws UnsupportedOperationException always
     * @deprecated Unsupported operation.
     */
    @CanIgnoreReturnValue
    @Deprecated
    @Override
    @DoNotCall("Always throws UnsupportedOperationException")
    public final E remove(int index)
    {
        throw new UnsupportedOperationException();
    }

    /**
     * Returns this list instance.
     *
     * @since 2.0
     * @deprecated There is no reason to use this; it always returns {@code this}.
     */
    @InlineMe(replacement = "this")
    @Deprecated
    @Override
    public final ImmutableList<E> asList()
    {
        return this;
    }

    @Override
    int copyIntoArray(@Nullable Object[] dst, int offset)
    {
        // this loop is faster for RandomAccess instances, which ImmutableLists are
        int size = size();
        for (int i = 0; i < size; i++)
        {
            dst[offset + i] = get(i);
        }
        return offset + size;
    }

    /**
     * Returns a view of this immutable list in reverse order. For example, {@code ImmutableList.of(1,
     * 2, 3).reverse()} is equivalent to {@code ImmutableList.of(3, 2, 1)}.
     *
     * @return a view of this immutable list in reverse order
     * @since 7.0
     */
    public ImmutableList<E> reverse()
    {
        return (size() <= 1) ? this : new ReverseImmutableList<E>(this);
    }

    private static class ReverseImmutableList<E> extends ImmutableList<E>
    {
        private final transient ImmutableList<E> forwardList;

        ReverseImmutableList(ImmutableList<E> backingList)
        {
            this.forwardList = backingList;
        }

        private int reverseIndex(int index)
        {
            return (size() - 1) - index;
        }

        private int reversePosition(int index)
        {
            return size() - index;
        }

        @Override
        public ImmutableList<E> reverse()
        {
            return forwardList;
        }

        @Override
        public boolean contains(@CheckForNull Object object)
        {
            return forwardList.contains(object);
        }

        @Override
        public int indexOf(@CheckForNull Object object)
        {
            int index = forwardList.lastIndexOf(object);
            return (index >= 0) ? reverseIndex(index) : -1;
        }

        @Override
        public int lastIndexOf(@CheckForNull Object object)
        {
            int index = forwardList.indexOf(object);
            return (index >= 0) ? reverseIndex(index) : -1;
        }

        @Override
        public ImmutableList<E> subList(int fromIndex, int toIndex)
        {
            checkPositionIndexes(fromIndex, toIndex, size());
            return forwardList.subList(reversePosition(toIndex), reversePosition(fromIndex)).reverse();
        }

        @Override
        public E get(int index)
        {
            checkElementIndex(index, size());
            return forwardList.get(reverseIndex(index));
        }

        @Override
        public int size()
        {
            return forwardList.size();
        }

        @Override
        boolean isPartialView()
        {
            return forwardList.isPartialView();
        }
    }

    @Override
    public boolean equals(@CheckForNull Object obj)
    {
        return Lists.equalsImpl(this, obj);
    }

    @Override
    public int hashCode()
    {
        int hashCode = 1;
        int n = size();
        for (int i = 0; i < n; i++)
        {
            hashCode = 31 * hashCode + get(i).hashCode();

            hashCode = ~~hashCode;
            // needed to deal with GWT integer overflow
        }
        return hashCode;
    }

    /*
     * Serializes ImmutableLists as their logical contents. This ensures that
     * implementation types do not leak into the serialized representation.
     */
    static class SerializedForm implements Serializable
    {
        final Object[] elements;

        SerializedForm(Object[] elements)
        {
            this.elements = elements;
        }

        Object readResolve()
        {
            return copyOf(elements);
        }

        private static final long serialVersionUID = 0;
    }

    private void readObject(ObjectInputStream stream) throws InvalidObjectException
    {
        throw new InvalidObjectException("Use SerializedForm");
    }

    @Override
    Object writeReplace()
    {
        return new SerializedForm(toArray());
    }

    /**
     * Returns a new builder. The generated builder is equivalent to the builder created by the {@link
     * Builder} constructor.
     */
    public static <E> Builder<E> builder()
    {
        return new Builder<E>();
    }

    /**
     * Returns a new builder, expecting the specified number of elements to be added.
     *
     * <p>If {@code expectedSize} is exactly the number of elements added to the builder before {@link
     * Builder#build} is called, the builder is likely to perform better than an unsized {@link
     * #builder()} would have.
     *
     * <p>It is not specified if any performance benefits apply if {@code expectedSize} is close to,
     * but not exactly, the number of elements added to the builder.
     *
     * @since 23.1
     */
    @Beta
    public static <E> Builder<E> builderWithExpectedSize(int expectedSize)
    {
        checkNonnegative(expectedSize, "expectedSize");
        return new ImmutableList.Builder<E>(expectedSize);
    }

    /**
     * A builder for creating immutable list instances, especially {@code public static final} lists
     * ("constant lists"). Example:
     *
     * <pre>{@code
     * public static final ImmutableList<Color> GOOGLE_COLORS
     *     = new ImmutableList.Builder<Color>()
     *         .addAll(WEBSAFE_COLORS)
     *         .add(new Color(0, 191, 255))
     *         .build();
     * }</pre>
     *
     * <p>Elements appear in the resulting list in the same order they were added to the builder.
     *
     * <p>Builder instances can be reused; it is safe to call {@link #build} multiple times to build
     * multiple lists in series. Each new list contains all the elements of the ones created before
     * it.
     *
     * @since 2.0
     */
    public static final class Builder<E> extends ImmutableCollection.ArrayBasedBuilder<E>
    {
        /**
         * Creates a new builder. The returned builder is equivalent to the builder generated by {@link
         * ImmutableList#builder}.
         */
        public Builder()
        {
            this(DEFAULT_INITIAL_CAPACITY);
        }

        Builder(int capacity)
        {
            super(capacity);
        }

        /**
         * Adds {@code element} to the {@code ImmutableList}.
         *
         * @param element the element to add
         * @return this {@code Builder} object
         * @throws NullPointerException if {@code element} is null
         */
        @CanIgnoreReturnValue
        @Override
        public Builder<E> add(E element)
        {
            super.add(element);
            return this;
        }

        /**
         * Adds each element of {@code elements} to the {@code ImmutableList}.
         *
         * @param elements the {@code Iterable} to add to the {@code ImmutableList}
         * @return this {@code Builder} object
         * @throws NullPointerException if {@code elements} is null or contains a null element
         */
        @CanIgnoreReturnValue
        @Override
        public Builder<E> add(E... elements)
        {
            super.add(elements);
            return this;
        }

        /**
         * Adds each element of {@code elements} to the {@code ImmutableList}.
         *
         * @param elements the {@code Iterable} to add to the {@code ImmutableList}
         * @return this {@code Builder} object
         * @throws NullPointerException if {@code elements} is null or contains a null element
         */
        @CanIgnoreReturnValue
        @Override
        public Builder<E> addAll(Iterable<? extends E> elements)
        {
            super.addAll(elements);
            return this;
        }

        /**
         * Adds each element of {@code elements} to the {@code ImmutableList}.
         *
         * @param elements the {@code Iterator} to add to the {@code ImmutableList}
         * @return this {@code Builder} object
         * @throws NullPointerException if {@code elements} is null or contains a null element
         */
        @CanIgnoreReturnValue
        @Override
        public Builder<E> addAll(Iterator<? extends E> elements)
        {
            super.addAll(elements);
            return this;
        }

        @CanIgnoreReturnValue
        Builder<E> combine(Builder<E> other)
        {
            addAll(other.contents, other.size);
            return this;
        }

        /**
         * Returns a newly-created {@code ImmutableList} based on the contents of the {@code Builder}.
         */
        @Override
        public ImmutableList<E> build()
        {
            forceCopy = true;
            return asImmutableList(contents, size);
        }
    }
}
